1. Field of the Invention
Aspects of the present invention relate generally to the field of distance measuring, and more particularly to a distance measuring system and method employing a laser distance sensor having utility in various applications.
2. Description of Related Art
Automatic or autonomous devices (i.e., robotic devices or robots) that can be used for home and commercial applications, such as cleaning, often must be operative to navigate around an environment with no, or minimal, input from a user or an operator. To be cost-effective for many home or commercial applications, conventional sensor systems enabling or facilitating robot navigation tend to be very simple. In that regard, primitive navigation systems cause conventional devices to ricochet around an operating environment inefficiently; these devices reactively carom off of obstacles and repeatedly re-visit areas that have already been treated, wasting valuable consumables and battery capacity. As an alternative, it may be desirable in some instances to implement a sophisticated sensor system in a way that serves a number of functions while minimizing or eliminating redundancies to maintain cost-effectiveness.
The foregoing co-pending United States patent applications provide, among other things, practical solutions to previously unresolved difficulties typically associated with navigation of robotic devices; the disclosed embodiments of distance sensor apparatus and methods have utility in numerous applications beyond robotic device navigation, however.
For example, many automobiles have recently been equipped with electronic distance measuring mechanisms to assist a driver attempting to park the vehicle. In some implementations, relatively rudimentary radar, ultrasound, infrared (IR) or other sensors may be employed, for example, at or near the rear bumper; when the vehicle is in a reverse gear, the sensors may measure distances to objects disposed in a “blind spot” or that might otherwise be difficult to observe from the driver's seat. Such systems typically employ an audible warning mechanism in which changes in tone or frequency, for example, may provide an indication of an obstacle's distance from the sensors. More sophisticated automated systems may employ various sensors that seek to enable an automobile to park itself automatically, i.e., without driver intervention, in some situations, such as during parallel parking.
Some automobile manufacturers are working to develop “smart cruise control” functionality, which attempts to control throttle and braking systems in order to maintain a safe following distance, for example, as a function of speed and other traveling conditions. With the recent introduction of high resolution display panels into automobile instrument clusters (to display various information from audio entertainment selections to detailed navigational information and global position system (GPS) data), it may be desirable in some instances to incorporate display of critical information relying upon distance measurements into automobiles and other vehicles.
Distance measuring equipment may have utility in connection with any type of moving vehicle and in any of various environments. In addition to the robot and automobile examples described above, for instance, a fork-lift operating in a warehouse may benefit from installation of accurate distance measuring systems, particularly since operator visibility may be restricted in many circumstances. Additionally, various types of sensing technology may have utility in stationary, or “fixed,” applications, i.e., where a fixed sensor is operative to detect motion in its operating environment. For example, some industrial safety systems may employ a “safety curtain” in which a sensor (or a sensor array) may provide a warning in the event that a person or moving equipment approaches dangerous machinery. In other examples, sensors or sensor arrays may be fixed at a turnstile, a safety check point, a toll-booth, or other area to be monitored; such systems may be employed to detect and to count people or vehicles passing through a particular area of space.
Typical distance measuring equipment is either too expensive to be practical for many applications or too large and cumbersome to be suitable for applications requiring a small form factor. Two popular laser distance sensor (LDS) devices that have limited potential for use in vehicular or other applications, the SICK LMS 200, currently marketed by SICK AG, and the Hokuyo URG-04LX, currently marketed by Hokuyo Automatic Co., Ltd., both cost an order of magnitude more than the simplest home and commercial robot cleaners, making them unsuitable for such uses. Additionally, these devices rely upon spinning mirrors for scanning operations, and consequently require attendant lenses and other optical components; the resulting large form factors and limited resolution and range tend to make most of these devices unsuitable for automotive or other large-scale applications.
Therefore, it may be desirable to provide a laser distance sensor system and method capable of acquiring accurate distance data in a compact, robust package.